<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div{
            width: 400px;
            height: 400px;
            /*确定边框的颜色 确定边框的粗细 确定边框的样式*/
            border: 3px solid red;
            /*border-left: #87ceed 5px dashed;
            border-bottom: #cd65e4 10px dotted;
            border-top: #7f8c8d 20px solid;
            border-right: #f5f5f5 14px dashed;*/
            /*边框圆角*/
            border-radius: 10px;
        }
    </style>
</head>
<body>
<div>

</div>
</body>
</html>